This invention relates to compositions of matter classified in the art of chemistry as epoxides or epoxy derivatives, more specifically, as 1,2 oxides derived from organic compounds having carbon to carbon unsaturated bonds, more specifically as epoxides of adducts of unsaturated fatty oils and still more specifically as epoxides of copolymers of dicyclopentadiene (DCPD) and unsaturated fatty oils having an original iodine number of at least about 70, to compositions containing them and to processes for their preparation and use.